Despite the availability of excellent antimicrobial drugs, the mortality from bacteremia remains high, especially when shock accompanies sepsis. Early administration of an appropriate antibiotic greatly improves the chances for survival of a patient suffering from bacteremia. It is thus imperative that the identification and susceptibility of the infecting organism be determined as early as possible in the course of bacteremia.
When conventional techniques are employed to identify an infecting organism, however, several days to as long as two weeks may be required for adequate growth and isolation of an organism contained in blood. This may be due to the administration of an antibiotic prior to drawing the blood sample for testing. The presence of the antibiotic in the blood can result in inhibition of the growth of bacteria, thus interfering with isolation and identification of the offending bacterium.
Bacteremia is associated with nosocomial procedures, being related to use of urinary catheters, respiratory and intravenous therapy and hyperalimentation. In these cases and others, where antibiotics may not be present in the blood, the isolation of the offending organisms still may require excess periods of incubation because of inhibitors contained in serum, plasma or lysed erythrocytes.
Bacteriuria is also difficult to establish when the patient has been placed on antibiotics and is excreting antibiotics in the urine along with the bacteria. Direct plating of urine for isolation of bacteria in such cases is usually ineffective since the inoculum also contains the antibiotic. Thus, culturing for the causative agent is often difficult due to the presence of antimicrobial agents.
Similar problems exist when other body fluids, such as spinal fluid, abscess exudates, and the like, are examined.
The present conventional method for detection of bacteria or fungi in cases of septicemia or for detection of bacteriuria or bacterial meningitis is to inoculate 5 ml of whole blood, urine or spinal fluid into a culture medium and wait for the appearance of turbidity, which manifests bacterial growth. Patients who have been on antibiotic therapy will have the antibiotic in their blood, urine or spinal fluid at the time the culture is initiated. The presence of the antibiotic will inhibit growth of the bacteria and may delay isolation of the offending organism for as long as 14 days and sometimes longer.
More rapid detection of bacteria in blood is presently possible by employing radioactive CO.sub.2 in the culture. Since bacteria metabolize CO.sub.2, the disappearance of the tagged carbon dioxide indicates the presence of bacteria. Although this method may rapidly determine the presence of bacteria in blood cultures in the absence of antibiotics or other inhibitors, it is inefficient when bacteriostasis occurs due to the presence of antibiotics or other inhibitors in the blood cultures.
Recent methods for the separation of antibiotics from bacteria by membrane chromatography have been reported, but these procedures are not presently practical because of the manipulations required and the high rate of contamination of the test cultures by exogenous organisms. Thus, rapid isolation and identification of bacteria in body fluid specimens is not possible using conventional methods where the specimen contains bacterial inhibitors.
Although resin exchangers and adsorbents are known to adsorb charged antibiotics from fluid specimens, they have not proven to be a satisfactory means for removing antibiotics from bacterially infected specimens where rapid isolation and identification of an infecting bacterium is the objective. The reason for this is that upon passage of a specimen containing an anionic antibiotic and an infecting organism through an anionic exchange resin, the resultant filtrate is not only substantially freed of the antibiotic, but the infecting bacteria are also significantly removed by the resin exchanger.
It is therefore an object of the present invention to provide a means for the rapid isolation and identification of an infecting organism in a body fluid specimen.
It is another object of this invention to provide a means for selectively removing bacterial inhibitors from body fluid specimens.
It is a further object of the present invention to provide a means for removing antibiotics from a bacterially infected body fluid specimen without significantly reducing the bacterial count of the specimen.
It is yet another object of the present invention to provide a resin which will adsorb charged antibiotics contained in a body fluid specimen while exhibiting diminished adsorption of bacteria from the specimen.
It is still another object of the present invention to provide a resin for removing materials inhibitory to bacteria from body fluid specimens while sparing a significant number of bacteria.